1. Field of the Invention
The invention relates to a surveillance device using a surveillance unit such as a video camera, the signals from which are received by a detection unit, the device being mounted on a mobile chassis driven by propulsion means inside a tube equipped with a longitudinal window through which passes the transverse axis of sight of the surveillance unit.
2. Description of the Prior Art
Such devices have proved particularly effective for the surveillance of large areas such as public places, stores, conference rooms or similar areas and even large parts of networks for example freeway systems.
The tube in which the surveillance unit moves can be extremely long, up to several miles if the propulsion means are appropriately designed.
However, it has proved in use that the longitudinal window through which the axis of sight passes can offer a number of disadvantages. It allows dirt and foreign bodies to penetrate necessitating costly maintenance and even risking causing breakdowns and failures. Moreover, the window must be closed if the propulsion means is a gas under high or low pressure.
A solution consisting in providing the window with a transparent glazed surface has been proposed and successfully tried but it is relatively expensive to produce and necessitates automatic glass cleaning means.